JP2002517902A - Cutting method of conductive link by ultraviolet laser output - Google Patents

Abstract

(57) [Summary] By utilizing the absorption characteristics of the materials constituting the conductive link (42), the lower semiconductor substrate (50), and the passivation layer (48 and 54), the substrate ( Efficiently remove link (42) without damaging 50). The short wavelength of the UV laser output creates a smaller link removal spot diameter (58) than conventional IR lasers, which allows higher circuit densities to be achieved. The passivation layer located between the link and the substrate is made sufficiently absorptive and thick enough for the UV laser energy so that the laser energy is attenuated so that the substrate (50) in the laser beam spot area (43) However, both the portion outside the link and the portion where the link overlaps can be prevented from being damaged. A UV laser output may be employed and controlled to ablate a depth portion of the passivation layer (54) under the link (42) to facilitate complete removal of the link (42). . In addition, direct ablation of the passivation layer (48) at the UV laser output facilitates link breakage to be predictable and consistent. Also, the absorbing properties of the passivation material reduce the risk of damage to adjacent links or other active structures.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to a laser-based method for cutting conductive links in integrated circuit devices fabricated on semiconductor wafers, and in particular, at a predetermined wavelength, located on a passivation layer. The present invention relates to a method of employing an ultraviolet laser output having a power density large enough to cut a link, wherein the passivation layer is high enough to prevent the laser output from penetrating into an underlying substrate. It is characterized by absorption sensitivity.

BACKGROUND OF THE INVENTION Laser links that can be cut by lasers, such as defective memory cells, are momentarily removed and disconnected to replace redundancy in memory devices such as DRAM, SRAM, or embedded memory. Conventional laser wavelengths of 1.047 μm or 1.064 μm have been employed for more than 20 years to replace cells. Similar techniques have been used to break links to program logic products, gate arrays, and ASICs. FIG. 1A illustrates a link structure 16 comprising a polysilicon or metal link 18 located above a silicon substrate 20 and between component layers of a passivation layer stack including an upper passivation layer 21 and a lower passivation layer 22. 1 shows a conventional infrared (IR) pulsed laser beam 12 with a spot size diameter 14. Silicon substrate 20 absorbs only a relatively small percentage of IR radiation, and conventional passivation layers 21 and 22, such as silicon dioxide or silicon nitride, are relatively transparent to IR radiation.

To avoid damaging the substrate 20 while maintaining sufficient energy to process the metal links 18, Sun et al. In US Pat. No. 5,265,114 used to process links 18 on silicon wafers. , It is proposed to use longer laser wavelengths, such as 1.3 μm. At a laser wavelength of 1.3 μm, the absorption contrast between the link material and the silicon substrate 20 is much greater than the conventional 1 μm laser wavelength. The wider laser processing window and better processing quality provided by this technique have been used in industry for about three years and have been very successful.

However, the IR laser wavelength has several disadvantages: the coupling efficiency of the IR laser beam 12 into the highly conductive metallic link 18 is relatively poor; The spot size 14 of the IR beam 12 is relatively large, which limits the critical length of the link width 24, the link length 26 between the contact pads 28, and the link pitch 30. IR laser link processing includes heating at link 18,
Relying on melting, which causes an increase in mechanical stress and momentarily opens the upper passivation layer 21. The failure behavior of the thermal stress depends somewhat on the width of the link 18. If the link width is smaller than 1 μm, the destruction pattern of the passivation layer 21 becomes irregular, resulting in inconsistent and unacceptable link processing quality.

[0005] The smaller laser spot size limit for the practically obtained link cutting laser beam 12, which is the basis for choosing the optical elements and their clearance from the substrate 20, is advantageously at its wavelength (2λ). Can be approximated by twice.
Thus, for laser wavelengths of 1.32 μm, 1.06 μm, and 1.04 μm, the actual spot size limits for link removal are approximately 2.6 μm, 2.1 μm, and 2.0 μm, respectively.
μm. The lower limit of the usable link pitch 30 is the laser beam spot 14
And the lower limit of the spot size directly affects the density of the circuit integration, as a function of the positioning accuracy of the laser beam 12 with respect to the target position of the link 18.

[0006] The spot size 14 of the minimally focused material removal laser currently used in the industry for repairing 64-Mbit DRAMs is about 2 μm in diameter. 2.1 μm spot size 14 is 256 Mbit and some 1 Gbit DR
It is considered useful through the design of AM. FIG. 2 shows a graph of spot size versus year, which represents the industrial demand for smaller spot sizes as link pitch 30 and link width 24 decrease. This graph is
It is based on a simplified formula that approximates the spot size demand: spot size diameter = 2 (minimum link pitch) −2 (system positioning accuracy) − (link width). (
These parameters are shown in FIG. 1B. This graph assumes 0.5 μm accuracy in 1997, 0.35 μm accuracy in 1999, and 0.25 μm accuracy thereafter. Therefore, industry experts predict that spot sizes of less than 2 μm will soon be promising for link processing. However, these spot sizes are not, in fact, obtainable with conventional link-breaking IR laser wavelengths.

At shorter visible wavelengths, such as 0.532 μm, the spot size of the laser beam can be reduced. However, these wavelengths are very easily absorbed by the silicon substrate 20, and a part of the substrate 20 is damaged by the laser link cutting process. To guarantee the reliability of the processed device, substrate damage is unacceptable.

Accordingly, a conductive link manufactured on a semiconductor wafer is cut at a laser wavelength selected so that the actual beam spot size is significantly less than 2 μm and the semiconductor wafer substrate is not damaged while cutting the link. A processing method and an apparatus are required.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a conductive link fabricated in an integrated circuit structure on a semiconductor wafer using ultraviolet (UV) laser output without damaging the lower wafer substrate. It is to provide a laser-based method of cutting a laser. Another object of the present invention is to reduce the coupling of laser output energy into the substrate during link cutting with a laser output parameter selected to take advantage of the wavelength-sensitive light absorption properties of a given link construction material. The aim is to provide a method that is implemented to:

[0010] The present invention provides a laser output beam in the UV wavelength range for cutting conductive links in an integrated circuit structure. This wavelength range is unconventional for link processing, and the present invention makes use of the light absorption properties that are sensitive to the wavelength of the passivation layer located between the link and the substrate. Since conventional passivation materials such as silicon dioxide and silicon nitride exhibit relatively high absorption of UV radiation, they absorb extraneous UV laser output energy and prevent this energy from damaging the substrate Can be adopted for. These and other passivation materials can be further optimized to better absorb suitable UV laser wavelengths.

More specifically, a layer of passivation material below the link absorbs the energy of the UV laser bombarding the integrated circuit structure and dissipates this energy to the link width and adjacent portions of the passivation layer where the links do not overlap. Is spread over the area of the beam spot size. Since the lower passivation layer absorbs UV light, this layer
The light can be attenuated so that this UV light is at the energy level required to break the link and does not damage the wafer substrate. Without the absorption of UV light by the lower passivation layer, off-link laser output energy incident on said neighbors during the link cutting process can cause substrate damage.

Further, the bottom of the link is a portion that is difficult to completely remove, and incomplete removal of this portion lowers the open circuit resistance after the link is cut. To ensure that the link is completely cut, the laser beam controller partially penetrates the UV laser, thereby forming a depression in the lower passivation layer and moving the entire link in the spot area in the depth direction. Facilitate complete removal. The controller determines the depth of the dimple by controlling the amount of laser energy used to perform the link cutting process. Also, the height of the passivation material can be adjusted to be sufficiently thick to absorb excess laser energy associated with link removal. This eliminates the risk of damaging the surrounding or underlying substrate material.

Another advantage of using UV wavelengths for link processing is the smaller spot size compared to the spot size generated at IR wavelengths. For example, a spot size of 0.5 μm beam for 212 nm wavelength can be achieved immediately, compared to a spot size of 2.5 μm beam for 1 μm wavelength. The smaller the size of the link features, the more densely packed IC devices can be manufactured.
For integrated circuit structures having a passivation layer over the link, another advantage of the present invention is that removal of the top passivation layer is not only due to increased thermal induced stress, but also due to the UV laser energy. This is also achieved by direct removal of the passivation layer. This phenomenon is consistent and accurate in opening the upper passivation layer, and is therefore effective in cutting very narrow link widths, without which link heating according to a conventional link cutting process would result in the upper part being cut off. When a fracture occurs in the passivation layer, an irregular fracture cross section is caused.

Yet another advantage of the present invention is that it absorbs a large amount of UV laser energy by the passivation material layer. In conventional IR link processing, adjacent links are typically damaged by laser energy reflected from the side of the link being processed.
This problem occurs more frequently as the pitch between links continues to decrease. However, the light reflected by the side of the link being cut with UV laser energy can be attenuated by the passivation material, thus greatly reducing the risk of damaging adjacent links or other circuit structures. be able to.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The method of the present invention facilitates the use of shorter wavelengths, such as wavelengths in the UV range, for link removal, thereby reducing the spot size of the laser beam. A wavelength equal to or shorter than 400 μm is 0.8 μm
Facilitates the generation of laser beam spot sizes less than. The wavelength dependent absorption properties of some common link materials are described below.

FIG. 3 graphically illustrates the light absorption properties of various materials that can be used for link 18, such as aluminum, nickel, tungsten, and platinum. Figure 3 is a compilation of the relevant parts of the graph of absorption properties found in "Handbook of Laser Science and Technology" Volume IV Optical Materials: Part 2 By Marvin J. Weber (CRC Rress, 1986). . FIG. 3 shows that metals such as aluminum, nickel, tungsten, and platinum generally absorb laser energy better at UV wavelengths than at IR wavelengths. The metal nitride (eg, titanium nitride) and other conductive materials used to form the conductive link 18 generally have similar light absorbing properties. However, the absorption coefficients of these materials are not as immediate as those of metals.

The good absorption of these link materials at wavelengths in the UV wavelength range, especially shorter than 300 μm, suggests that these materials can be easily processed by UV laser power. This, in addition to the spot size advantage, the UV laser output results in much better coupling efficiency with the conductive link, more perfect link removal, better open resistance quality between disconnected links, And higher link processing yields are achieved.

[0018] Also disadvantageously, many semiconductor substrates are more susceptible to damage by laser output having a wavelength shorter than 1 μm. The absorption characteristics of some common substrate materials are described below.

FIG. 4 is a graph showing the light absorption coefficient with respect to laser photon energy (wavelength) for some arsenic compound concentrations in silicon. FIG. 4 is a duplicate of the diagram on page 1414 of Jellison et al., Phys. Rev. Let., Vol 46, 1981. FIG.
At wavelengths shorter than μm, both the absorption coefficients of doped silicon and undoped silicon show a steep increase. For physical details of this behavior, see
"Pulsed Laser Processing of Semiconductors", Semiconductors and Semimetals, Vol. 23 (Academic Press, 1984).

[0020] Reliable published values for the light absorption properties of doped polysilicon, polycide, disilicide (disilicide) with respect to wavelength are not immediately available, but those skilled in the art will appreciate the absorption of these doped materials. It is also believed that the coefficient can increase significantly at wavelengths shorter than 1 μm.

FIG. 5 graphically illustrates the light absorption coefficient versus wavelength for various semiconductors, including gallium arsenide and silicon, at room temperature. FIG. 5 is a copy of FIG. 156 of "Handbook of Optics", Walter G. Driscolled., Optical Society of America (McGraw-Hill Book Co., 1978). This graph shows that at room temperature, the light absorption properties of silicon, gallium arsenide, and other semiconductor materials increase dramatically at wavelengths in the visible and UV ranges over wavelengths in the IR range. As shown in FIGS. 4 and 5, the good absorption of wavelengths in the UV range by these substrates indicates that these substrates
It suggests that it is susceptible to damage by V laser output.

FIG. 6A is a graph showing the light absorption coefficient of quartz glass (silicon dioxide) with respect to wavelength. FIG. 6A shows "CMRandall and R. Rawcliff, Appl. Opt. 7: 213 (1968
Excerpted from the year). This graph shows that at wavelengths below about 300 μm, silicon dioxide shows good absorption properties, and at wavelengths below 200 nm, its absorption behavior increases dramatically. One skilled in the art is aware that the passivation layer of silicon dioxide is usually doped, either intentionally or as a result of diffusion from a doped wafer. Typical dopants include Group III and Group V elements, such as boron, phosphorus, arsenic, and antimony. Also, the passivation layer of silicon dioxide usually contains defects. Due to doping and / or defects, the passivation layer of silicon dioxide or silicon nitride becomes relatively well absorbing at longer wavelengths, such as less than or equal to about 400 nm. One skilled in the art will recognize that the particular dopant and its concentration can be adjusted to "tune" the passivation layer to better absorb the desired UV laser wavelength.

FIG. 6B graphically illustrates light transmission range versus wavelength for some crystalline optical materials, including silicon nitride. FIG. 6B is a reproduction of FIG. 5.1 of Chapter 4 of the Handbook of Infrared Optical Materials, Paul Klocek (copyright) Marcel Dekker, Inc., NY 1991. FIG. 6B shows that the transmittance of silicon nitride decreases at wavelengths shorter than about 300 nm.

FIG. 7A is a partially enlarged top view of a wafer 38 having a semiconductor link structure 40 of the present invention, and FIG. 7B is a spot region 43 of a laser pulse 44 characterized by a pulse parameter of the present invention. FIG. 7C is a partial cross-sectional side view of the link structure 40, and FIG. 7C is a view of FIG.
FIG. 2 is a partially enlarged side sectional view of the link structure 40 of FIG. As shown in FIGS. 7A to 7C, the link structure 40 includes a link length 46 and a link width 4 between the contact pads 52.
Preferably, it includes a metallic or conductive link 42 having a seven. Link width 4
7 can be designed to be less than the width 24 (about 2.5 μm) of the link 18 removed by the conventional IR link removal laser beam 12. Link materials include aluminum, copper, nickel, tungsten, platinum, and gold, as well as other metals, alloys such as nickel chromium, metals such as titanium nitride or tantalum nitride, and metals such as tungsten silicide. It can include, but is not limited to, silicides and doped polysilicon and similar materials. The link structure 40 can have a conventional size, but the link width 47 can be, for example, less than or equal to about 1.0 μm. Similarly, the distance 49 between the centers of the links 42 can be much smaller than the pitch 30 (about 8 μm) between the links 18 removed by the beam 12. The link 42 can be, for example, within 2.5 μm from other links 42 or adjacent circuit structures.
If a beam with a spot size of 2 12 nm equal to or less than about 0.5 μm is used to cut the link 42, the pitch 49 can be equal to or less than about 1.0 μm.

The link structure 40 typically includes a UV absorbing passivation layer 48 overlying the link 42. However, those skilled in the art will recognize that link 42 can be uncovered. Further, the link structure 40 is provided between the substrate 50 and the link 42.
A V-absorbing passivation layer 54 is included.

The passivation layer 54 preferably has a height 56 sufficient to attenuate the laser energy used to cut the link 42 by a sufficient amount so that the substrate 50 is not damaged. . Preferably, for a passivation layer 54 of silicon dioxide or silicon nitride, the height 56 is at least about 0.5 μm, more preferably about 0.8 μm. In particular, the height 56 of the passivation layers 48 and / or 54 is such that the off-link portions of these passivation layers and the portions 57 in the spot region 43 sufficiently attenuate the energy from the pulses 44 to link the substrate 50 It can be adjusted to protect the external component from damage. Passivation layers 48 and 54 can be of the same or different materials. The passivation layer 48 and / or 54 has a thickness of 300 nm.
At longer UV wavelengths, such as between 400 and 400 nm, it can be doped to increase absorption.

In addition to the benefits of utilizing UV described above, passivation layer 54 provides other advantages in processing. As shown in FIG. 7B, the height 56 can be adjusted so that the passivation layer 54 can be intentionally removed. Partial removal of the passivation layer 54 helps to completely remove the bottom of the link 42 without risk of damaging the substrate 50 and to provide a high open resistance between the contact pads 52.

FIG. 8 shows a preferred embodiment of a simplified laser system 120 that generates the desired laser pulses to achieve a UV link break according to the present invention. For convenience of explanation, the laser system 120 is modeled here only by the example of a fourth harmonic Nd: YAG laser pumped by a laser diode 110, the emission 112 of which is emitted by a lens component 114 by an IR laser. Resonator 1
22. The IR laser resonator 122 includes a rear mirror 126 and an output mirror 128
And a laser medium 124 located along the optical axis 130, which emits an IR pulse output 123 at a wavelength of 1064 nm having a characteristic pulse width of less than 10 ns at half-wave height full width. Mirror 126 is preferably 100% reflective to the fundamental wavelength of Nd: YAG and highly transmissive to the output of diode laser 110, and mirror 128 is preferred to the fundamental wavelength of Nd: YAG. Preferably, it has a reflectance of 100% and a high transmittance for the second harmonic light propagating along the optical axis 130. The internal resonance frequency doubler 134 is preferably located between the laser medium 124 and the output mirror 128. The quadrupler 138 is preferably provided outside the resonator 122 in order to further convert the frequency of the laser beam to a fourth harmonic.

The laser system also uses another nonlinear crystal to combine the fundamental wave and the fourth harmonic, or the second harmonic and the third harmonic to combine the fifth harmonic with the fifth harmonic. (212 nm for Nd: YAG, 210 nm for Nd: YLF). The harmonic conversion process is described in VGDmitriev et al., "Handbook of Nonlinear Optical Crystals", Springer-Verlag, New York, 1991, ISBN 3-540-53547-0, pages 138-141.

Alternatively, the IR laser resonator 122 has a N wavelength of 1.047 μm.
It can be a d: YLF laser or a Nd: YVO ₄ laser with a fundamental wavelength of 1.064 μm. Those skilled in the art also recognize that third harmonics of Nd: YAG (355 nm) and Nd: YLF (349 nm) can be employed to treat the link 42 surrounded by the doped passivation material. Those skilled in the art also recognize that other suitable lasers emitting wavelengths shorter than 300 nm are commercially available and can be employed. Modification of the laser system, such as the Model 9300 series manufactured by Electro Scientific Industries of Portland, Oregon, is a suitable adaptation for those skilled in the art to provide shorter wavelength UV lasers.

The laser system output 140 can be operated by various conventional optical components 142 and 144 provided along the beam path 146. Component 14
2 and 144 may include a beam expander or other laser optics that collimates the UV laser output 140 to produce a beam with useful propagation characteristics. The beam reflectors 172, 174, 176 and 178 have high reflectivity for the fourth harmonic wavelength of the UV laser, but high transmittance for the second harmonic of Nd: YAG, and Only the fourth harmonic UV reaches the surface 51 of the link structure 40. The focusing lens 148 focuses the collimated UV pulse output 140 to produce a focused lens size 58 of F1, F2, or F3 that is significantly less than 2 μm, and preferably less than 1 μm. It is preferable to use The focused laser spot 43 is directed onto the wafer 38 with the link structure 40 as a target, and preferably removes the link 42 with a single pulse 44 of UV laser output 140. By selecting the energy of the pulse 44, the depth at which the pulse 44 applied to the link 42 cuts can be accurately calculated and controlled. In general, the preferred ablation parameters for the focused spot size 58 are 1 ns at 1-5 kHz.
A pulse 44 having a duration of 100100 ns, preferably 5 kHz and 15 ns, includes a pulse energy between 0.01 J and 10 J.

A suitable beam positioning system is described in detail in US Pat. No. 4,532,402 to Overbeck. The beam positioning system 160 includes at least two platforms or stages and a number of mirrors 172, 174, 17
Preferably, a laser controller 170 is used to control lasers 6 and 178 to focus the laser system output 140 against the desired laser link 42 on the wafer 38. The beam positioning system 160 allows for rapid movement between the links 42 on the same or different chips to provide a uniform link disconnection operation based on provided test or design data. The position data preferably directs one pulse of the laser system output 140 to each of the separate links 42 at a time.

As shown in FIG. 8, for modulation of the intracavity laser beam using the Q-switch 180, the ignition of the laser system 120 is controlled by US Pat. No. 5,453,594, Konecny, inventor, “Radiation Beam Position and Timing data synchronized with the movement of the platform as described in "Emission Coordination System" can affect the laser controller 170. Alternatively, those skilled in the art will recognize that laser controller 170 can be used for out-of-cavity modulation of continuous wave (CW) laser energy via a Pockels cell or a photoacoustic device. This alternative can provide constant peak power regardless of the chopping repetition rate or the duration of the output pulse. Beam positioning system 160 may alternatively or additionally employ the improved method or beam positioner described in U.S. Pat. No. 5,751,585 to the assignee of the present invention, Cutler et al.

For a Q-switched pulsed solid state UV laser with nonlinear frequency conversion, U
The power level from pulse to pulse of the V output is particularly sensitive to the repetition rate or time interval between successive pulse firings. FIG. 9A shows a conventional UV
5 is a graph of UV laser energy per pulse versus time interval between pulses of the laser system. In a preferred embodiment, the optical modulator (OM) 181 is
38 and the optical element 142. The system 120 pre-checks for changes in UV energy per pulse change such that the time between pulses is different to establish an energy curve. Then, a "correction" signal is generated based on the energy curve information and supplied to the OM 181. FIG. 9B is a graph showing the correction signal supplied to the OM 181 to compensate for each time interval. Whenever the laser pulse 44 is fired, this correction signal is triggered,
The control signal voltage on the OM 181 changes with the elapsed time after the ignition of the immediately preceding laser pulse. Whenever the next laser pulse is fired, the correction signal on OM 181 will remain at a preset constant level, regardless of the time interval between any two consecutive laser pulses 44, regardless of the time interval between the correction signals. So that FIG. 9C is a diagram of the UV energy pulse after being modified by the OM 181. Those skilled in the art have recognized that in spite of the different time intervals between the pulses, this method allows the highest system positioning speed to be achieved without changing the UV laser energy per pulse.

Those skilled in the art will recognize that portions of the present invention may be implemented differently than the preferred embodiment described above. For example, the system control computer 170, the OM controller 171 and the beam positioning controller 160 may be combined into a single processor, or hard-wired digital logic, a program executed by a single processor, a microprocessor, It can be implemented as a state machine, or some combination of analog circuits.

It will be apparent that those skilled in the art can make numerous modifications to the details of the embodiments of the invention described above without departing from the principles of the invention.

[Brief description of the drawings]

FIG. 1A is a partial cross-sectional view of a conventional semiconductor link structure receiving a laser pulse with a conventional pulse parameter, and FIG. 1B is a cross-sectional view of the link width, pitch, and pitch described in connection with FIG. 1A. FIG. 3 is a diagram showing a mutual relationship between parameters of a spot size of a laser beam together with a structure of an adjacent circuit.

Fig. 2 Predicts the laser spot size required for the link process over time.
It is a graph of spot size / year.

FIG. 3 is a graph showing light absorption characteristics of four types of metals with respect to wavelength.

FIG. 4 is a graph showing the light absorption coefficient with respect to laser photon energy (wavelength) for some arsenic compound concentrations in silicon.

FIG. 5 is a graph showing the light absorption characteristics of various semiconductors with respect to wavelength at room temperature.

FIGS. 6A and 6B are graphs showing the light absorption characteristics of conventional passivation materials, particularly silicon dioxide and silicon nitride, with respect to wavelength.

7A is a partially enlarged top view of the semiconductor link structure of the present invention together with adjacent circuits, and FIG. 7B is a partially enlarged view of the link structure of FIG. 7A receiving a laser pulse according to the pulse parameter of the present invention. FIG. 7C is a cross-sectional view, and FIG. 7C is a side cross-sectional view of the link structure of FIG. 7B after removing the link with a laser pulse of the present invention.

FIG. 8 is a schematic diagram of one preferred embodiment of a UV laser system including a wafer positioner cooperating with a laser processing control system for performing the method of the present invention.

FIG. 9A shows the change in energy per pulse of a conventional UV laser output.
FIG. 9B is a graph shown as a function of the time interval between pulses, and FIG. 9B is a graph of a voltage correction signal applied to stabilize the energy per pulse of the UV laser output that occurs at variable time intervals; 9C is a graph showing the energy per pulse of the UV laser output of the present invention corrected for instability associated with variable time intervals between pulses.

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SL, SZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AL, AM, AT, AU, AZ, BA, BB, BG, BR , BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS , JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, US, UZ, VN, YU, ZA, ZW (72) Inventor Edward Svenson 97225 PO, United States of America Oregon Georgia South West Summit Coat 970 F Term (Reference)

Claims (31)

[Claims] 1. A method for cutting a conductive link fabricated on a semiconductor substrate in a link structure of an integrated circuit including an upper surface and a passivation layer, wherein the passivation layer is located between the link and the substrate. The link has a link width and the passivation layer has a height and wavelength sensitive light absorbing property, the method characterized by: a power density distributed in a spot area on an upper surface of the link structure. Generating an ultraviolet laser output of a predetermined wavelength having a predetermined energy and directing it to the link structure, wherein the spot area covers the link width and the adjacent portion of the passivation layer where the links do not overlap. The power density is large enough to cut the link, and the power density is Due to the light absorption properties and height responsive to the wavelength of the passivation layer, together with the predetermined wavelength interacting with the passivation layer, the adjacent portion of the passivation layer where the link does not overlap during the cutting of the link becomes the adjacent portion. A method of cutting a conductive link, comprising: attenuating off-link energy of the laser output incident on a portion so that the laser output does not damage the substrate. 2. The method of claim 1, wherein said predetermined wavelength of said laser output is less than about 300 nm. 3. The method of claim 2, wherein the predetermined wavelength of the laser output is about 266 nm, about 262 nm, about 212 nm.
3. The method of claim 2, wherein the thickness is about 210 nm, or about 193 nm. 4. The method of claim 1, wherein generating the ultraviolet laser output further comprises forming a pulsed ultraviolet laser output by optically pumping a Q-switched ultraviolet emitting solid state laser. 3. The method according to 3. 5. The method of claim 1, wherein said passivation layer comprises silicon dioxide or silicon nitride. 6. The method of claim 5, wherein the height of the passivation layer is at least about 0.5 μm. 7. The link of claim 1, wherein the link is one of a number of conductive links fabricated on the substrate spaced apart from each other by a pitch distance of less than about 2.5 μm. the method of. 8. The method of claim 1, wherein said link width is less than or equal to about 1.0 μm. 9. The method of claim 1, wherein said spot area has a diameter of less than about 2.0 mm. 10. The laser output removes a portion of the passivation layer under the link, such that substantially all of the link within the spot area is removed and under the link. The method of claim 1, wherein the substrate is not damaged. 11. The link structure further comprising an uppermost passivation layer located above the link, wherein the uppermost passivation layer is directly ablated by the ultraviolet laser power cutting the link. The method of claim 1, wherein the method comprises: 12. The method of claim 1, wherein said link forms a part of a memory device or ASIC. 13. The method of claim 1, wherein said passivation layer is doped to increase absorption at said predetermined wavelength. 14. The method of claim 1, wherein said predetermined wavelength of said laser output is about 349 nm or about 355 nm. 15. The passivation layer underneath the link attenuates the energy of the laser output beyond what is required to cut the link so that the substrate under the link is not damaged. The method of claim 1 wherein the method comprises: 16. The link is one of a number of conductive links fabricated on the substrate, the links being separated from one another by a passivation material having wavelength sensitive light absorbing properties. The passivation material then attenuates the energy of the laser output reflected at the first of the links toward the second link so that the laser output does not damage the second link. The method of claim 1, wherein: 17. A method for cutting a first conductive link fabricated on a semiconductor substrate, the first link being separated from the second conductive link by a passivation material, wherein the passivation material is separated from the second link. Having a wavelength-sensitive light absorbing property located between the second links, the method comprising: having energy characterized by a power density large enough to sever said links; Generating an ultraviolet laser output of a predetermined wavelength and directing it to the first link, wherein the power density is coupled with the predetermined wavelength interacting with the passivation material, and a light absorption responsive to the wavelength of the passivation material. The passivation of the energy of the laser output reflected by the first link towards the second link, depending on the characteristic; Fee attenuates, the method of cutting a conductive link the laser output is characterized by something like not to damage the second link. 18. The method of claim 17, wherein said predetermined wavelength of said laser output is less than about 300 nm. 19. The method of claim 17, wherein the first and second links are separated by a pitch distance of less than about 2.5 μm. 20. A method of cutting a conductive link between a pair of conductive contact pads fabricated on a semiconductor substrate in an integrated circuit link structure, wherein the integrated circuit link structure comprises a link between the link and the substrate. A passivation layer positioned thereon, the passivation layer having height and wavelength sensitive light absorbing properties, the method comprising: ultraviolet light having a predetermined wavelength interacting with the wavelength sensitive light absorbing properties of the passivation layer. Generating a laser output and directing the laser output to the link structure, cutting the link to form a depth hole in the passivation layer below the link; Forming a high open electrical resistance between them,
A method of cutting a conductive link, wherein the laser output does not damage the substrate under the link due to the height of the passivation layer and the wavelength-dependent light absorption characteristics. 21. The method of claim 20, wherein said predetermined wavelength of said laser output is less than about 300 nm. 22. The method of claim 21, wherein said predetermined wavelength of said laser output is about 266 nm, about 262 nm, about 212 nm, about 210 nm, or about 193 nm. 23. The method of claim 20, wherein said predetermined wavelength of said laser output is about 349 nm or about 355 nm. 24. The method of claim 11, wherein the uppermost passivation layer is doped to increase absorption at the predetermined wavelength. 25. The method of claim 17, wherein the passivation material is doped to increase absorption at the predetermined wavelength. 26. The method of claim 17, wherein said predetermined wavelength of said laser output is about 349 nm or about 355 nm. 27. The method of claim 18, wherein said predetermined wavelength of said laser output is about 266 nm, about 262 nm, about 212 nm, about 210 nm, or about 193 nm. 28. The method of claim 1, wherein the predetermined wavelength of the laser output comprises a third harmonic of a fundamental wavelength generated by a Nd: YLF laser. 29. The method of claim 17, wherein the predetermined wavelength of the laser output comprises a third harmonic of a fundamental wavelength generated by a Nd: YLF laser. 30. The method of claim 20, wherein the predetermined wavelength of the laser output comprises a third harmonic of a fundamental wavelength generated by a Nd: YLF laser. 31. The method of claim 9, wherein the spot area has a diameter of less than about 1.0 μm.